(1) Field of the Invention
The invention relates to amphibious vehicles, particularly to amphibious vehicles for use in dredging, and more particularly to restoring wetlands using amphibious dredging vehicles.
(2) Description of the Related Art
Amphibious vehicles, sometimes called marsh buggies, were first developed about fifty years ago. The early vehicles were often used to transport persons and equipment through marshes for oil-and-gas exploration.
First-generation amphibious vehicles have two engines powering four large hollow wheels. The wheels are made of lightweight steel to provide both buoyancy and durability. Each wheel has deep, lugged cleats for traction.
Second-generation amphibious vehicles incorporate pontoons and track-drive systems. These second-generation amphibious vehicles include two longitudinal pontoons for buoyancy and at least one continuous drive track surrounding each pontoon for drive power. Each drive track includes an endless chain driven by a hydraulic motor through a sprocket, and each chain carries channel-type cleats for traction. These conventional vehicles are common in the art of amphibious vehicles. For example, see U.S. Pat. No. 5,984,032 to Gremillion et al.
Both first-generation and second-generation amphibious vehicles move in shallow water by gripping the water bottom with their cleats and rolling or tracking forward. (In this patent application “shallow water” means water in which the cleats of a conventional amphibious vehicle can grip the water bottom; and “deeper water” means water in which the cleats of a conventional amphibious vehicle float above the water bottom and cannot grip it.) In deeper water, conventional amphibious vehicles move by paddling the water with their cleated wheels or cleated tracks. The wheels or tracks are driven just as they are on land or in shallow water, and the vehicle moves by the force created by moving the wheels or tracks through the water. These vehicles move through deeper water inefficiently and slowly.
Cutterhead dredges are useful for restoring degraded wetlands. In restoring wetlands, cutterhead dredges can be used to rebuild land in water-covered areas where erosion has occurred. Applicant's U.S. patent application Ser. No. 10/349,599, which is incorporated herein by reference, discloses a system and method for restoring degraded wetlands using a cutterhead dredge and other devices.
Cutterhead dredges intended for use in wetlands are commonly mounted either on a floating vessel—typically a boat or a barge—or on a conventional amphibious vehicle. Whether mounted on a floating vessel or on an amphibious vehicle, cutterhead dredges work well in the areas that they can reach. But both floating vessels and conventional amphibious vehicles cause problems when one dredging task is complete and the operator needs to move the dredge to a new location. Floating vessels cannot travel over land; conventional amphibious vehicles travel across water inefficiently and slowly.
Floating vessels are limited to areas where there is enough water to float the particular vessel—preferably without undue risk of running aground. Because wetlands restoration often takes place in a degraded marsh—a combination of land, water too shallow for most vessels, and deeper water—floating vessels simply cannot reach many areas that need to be restored. Further, in many wetlands that need to be restored, cutting a channel for a floating vessel would be expensive and counterproductive.
Unlike floating vessels, conventional amphibious vehicles can travel on land or in shallow water. But in deeper water, where their cleats cannot grip the bottom, conventional amphibious vehicles move so slowly that driving them a substantial distance across deeper water becomes impractical. The user must choose between driving the conventional amphibious vehicle slowly across the deeper water or finding another way—usually transport by vessel or truck—to move the vehicle where it needs to be. When a vessel or truck can be used to transport a conventional amphibious dredging vehicle, the transportation requires substantial additional equipment (and thus substantial additional cost) when compared to the applicant's amphibious dredging vehicle.
Further, many wetlands that need restoring simply cannot be reached conveniently by vessel or by truck. Accessing these areas forces the user of a conventional amphibious vehicle to endure the long, slow, unproductive trip to the dredging area from the closest point of access.
Applicant's invention improves on the prior art by using the pumping capacity of a cutterhead dredge to increase a conventional amphibious vehicle's speed and maneuverability in deeper water. The applicant's amphibious dredging vehicle provides greater speed and maneuverability in deeper water than a conventional amphibious vehicle provides. And using applicant's invention, a cutterhead dredge can be moved across land or shallow water as if mounted on a conventional amphibious vehicle. In sum, when compared to dredges mounted on conventional amphibious vehicles, applicants' amphibious dredging vehicle provides equal performance on land or in shallow water and superior performance in deeper water.
In a degraded marsh that includes land, shallow water, and deeper water that must all be crossed for the dredge to do its work, applicant's invention allows for faster, more efficient, and more convenient restoration than is possible using a dredge mounted on a floatable vessel or on a conventional amphibious vehicle.
Applicant's invention provides an amphibious dredging vehicle with improved mobility in deeper water. In embodiments of applicant's invention in which only a single directable discharge is present, the amphibious dredging vehicle has this advantage when the vehicle is being moved from one dredging area to a second dredging area—with no dredging performed during the trip from the first dredging area to the second. When a single-directable-discharge embodiment of the amphibious dredging vehicle is dredging (actually removing material), the directable discharge normally will be unavailable for propulsion. The directable discharge cannot normally be used for propulsion during material removal because normally the dredging plan will require the dredged material to be deposited in a particular area by means of piping connected to the dredge discharge. When piping is connected to the directable discharge of an amphibious dredging vehicle that has a single directable discharge, the directable discharge cannot provide propulsion to the amphibious dredging vehicle.
On the other hand, if the amphibious dredging vehicle is equipped with a second directable discharge that is not connected to the dredge cutterhead so as to discharge dredged material, then the second directable discharge may be used for propulsion while the cutterhead is being used to remove and deposit dredged material.